Dialysis therapy: Kidney to go?

28. September 2015
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Researchers are working on developing a portable artificial kidney and the first clinical trials with prototypes have delivered very promising results. There are still technical hurdles that need to be overcome before this device for safe dialysis can go into mass production. But the need is great.

At this year’s Dialysis Conference of the American Society of Nephrology, participants had the chance to take a look at the not-so-distant future. Dr Victor Gura, professor at the University of California in Los Angeles, presented his progress in the development of a wearable artificial kidney (known by its acronym as the “WAK”). Initial clinical trials in Italy and the UK have already been completed [Paywall] and the first study is now underway in the United States with support from the FDA’s innovation programme designed to accelerate the development of medical devices.

The WAK as presented at the conference is a battery-operated, miniaturized dialysis unit that can be worn by the patient like a tool belt. The prototype weighs 4.5 kg and only requires about 400 ml of sterile water, representing a major step forward from conventional dialysis machines that normally weigh 60 kg or more and consume about 120 litres of water. The WAK’s absorption cartridge combining urease, activated carbon, zirconium phosphate, and zirconium oxide to remove uremic substances and salts.

Despite promising first studies, there are technical questions that still need to be clarified: for example, what influence do the ion exchange absorbers have on the electrolyte and acid-base balance and the safety of direct blood circulation access. If there is an accidental separation, for example, there is a risk of substantial blood loss and air embolism. Consequently, the dream of the artificial kidney will not be quite as quickly realised as one might hope. But Dr Gura remains optimistic: “I hope that in five years this equipment will be used across the country.”

Dialysis machine as the last resort

For patients with severe kidney disease, dialysis is often the last hope, because the chances of obtaining a kidney transplant are low. An example from Germany: According to statistics from the German Organ Transplantation Foundation (DSO) , a total of 2,128 kidney transplants were performed in 2014, with 1,508 of the kidneys coming from post-mortem organ donations. But there are some 8,000 patients currently on the waiting list. These patients need uremic substances removed from their blood via some form of renal replacement therapy, but none of the current dialysis procedures are currently able to replace the full function of the kidneys.

The biggest drawback of haemodialysis is that it is usually performed only three times a week, which results in large fluctuations within the body. Although peritoneal dialysis allows for more continuous cleansing of the blood, the removal of uremic toxins is, however, not very efficient and will, in the long term, lead to damage of the peritoneal membrane due to the high intraperitoneal glucose concentrations that are necessary to establish an osmotic gradient.

An analysis of national registers, such as the United States Renal Data System (USRDS) , has shown that the life expectancy for dialysis patients is markedly lower than that of the general population. Daily home-based haemodialysis therefore appears to be superior over conventional haemodialysis and not only can improve the survival rate, but also improve the patients’ quality of life, nutritional status, and the number of pills needed. However, only a small part of all dialysis patients will be treated with home haemodialysis. Even if they do get access to this treatment, they will still be bound for many hours every day to a large medical device. They will not be mobile and going on holiday is, of course, out of the question. The wearable artificial kidney therefore seeks to ensure efficient removal of toxins and a slow exchange of liquids while allowing high mobility and flexibility.

Global supply and demand

While the first WAK prototypes are still wrestling with the technical challenges of safety, operation, and efficiency, a review article published in The Lancet (March 2015) concluded that there is a great need for cost-effective methods for the treatment of renal failure, since, at best, only half of those who need renal replacement therapy or a transplant receive it. In the year examined (2010), at least 2.3 million people in need of treatment died prematurely because of this lack of treatment. “The large number of deaths occurring because of poor access to treatment sets a demanding task for the nephrology community and the health-care and research communities in general,” declared the lead author of the review article, Professor Vlado Perkovic of the University of Sydney.

The review article indicates that the availability of treatment is particularly critical in Asian and African countries with low- and middle per capita income, for example, Nigeria, Pakistan, Indonesia, India and China, where less than a quarter of patients with renal insufficiency receive the necessary treatment. In one comment to The Lancet article, Professor Josef Coresh of Johns Hopkins University and Professor Tazeen Jafar from the Duke-NUS Graduate Medical School in Singapore push for solutions to meet this need, such as the wearable artificial kidney could one day be: “The time has come to include treatment of kidney failure, and its prevention by detection and management of chronic kidney disease, in the global health agenda.”

 

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